Re: [Phys-L] e/m apparatus

[Peter Schoch <pschoch@fandm.edu>]

OK, now that I've stopped laughing (over the "electron porn" phrase), I can
say thank you for the reference as well as the great laugh!

Also, to bc -- the error if alignment was ignored and the apparatus just
set-up "haphazardly" was nearly 58%.  If everything was set up just as
specified, etc. we could never get the error below 30%.

I guess my bottom-line was that I would not buy the apparatus.  (I
'inherited' this one from the former Physics Prof. here -- and like many
other 'flashy toys' he had ordered, I wish I hadn't.)

Peter

On Wed, Jun 7, 2017 at 3:08 PM, John Denker via Phys-l <
phys-l@mail.phys-l.org> wrote:

> On 06/07/2017 11:45 AM, Peter Schoch wrote:
>
> > I have the second one, and it gives abysmal results.
>
> Here is perhaps another way of looking at this situation.  There
> is a scientific proverb that says:
>  -- Some things are easier to see than to measure.
>  -- Some things are easier to measure than to see.
>
> Let me explain:  Consider the chemistry demonstration that creates
> a huge billowing colored flame, using a squirt bottle and a solvent
> with some dissolved ions.  It makes for an attention-grabbing demo,
> but if you wanted to do serious spectroscopy you wouldn't do it
> that way.
>
> I put Teltron tubes in the same category.  They are a flashy way of
> showing that electrons exist, but if you really wanted to measure
> something you wouldn't do it that way.\1\  To this way of thinking,
> a Teltron tube should not be called "e/m apparatus";  perhaps a
> better name would be "electron porn".
>
>
> Reference:
>
> \1\  T. D. Whyte, N. P. J. Rymills, and J. S. Willis,
>   "Measurement of e/m0 using Dunnington’s method—An experiment for
> advanced undergraduates"
>   American Journal of Physics 52, 706 (1984)
>   http://dx.doi.org/10.1119/1.13574
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